Effect of collisions on dust particle charging via particle-in-cell Monte-Carlo collision

Abstract

In this paper, the effect of collisions on the charging and shielding of a single dust particle immersed in an infinite plasma is studied. A Monte-Carlo collision (MCC) algorithm is implemented in the particle-in-cell DEMOCRITUS code to account for the collisional phenomena which are typical of dusty plasmas in plasma processing, namely, electron-neutral elastic scattering, ion-neutral elastic scattering, and ion-neutral charge exchange. Both small and large dust particle radii, as compared to the characteristic Debye lengths, are considered. The trends of the steady-state dust particle potential at increasing collisionality are presented and discussed. The ions and electron energy distributions at various locations and at increasing collisionality in the case of large particle radius are shown and compared to their local Maxwellians. The ion-neutral charge-exchange collision is found to be by far the most important collisional phenomenon. For small particle radius, collisional effects are found to be important also at low level of collisionality, as more ions are collected by the dust particle due to the destruction of trapped ion orbits. For large particle radius, the major collisional effect is observed to take place in proximity of the presheath. Finally, the species energy distribution functions are found to approach their local Maxwellians at increasing collisionality.

Basic Processes in Complex (Dusty) Plasmas: Charging, Interactions, and Ion Drag Force

“…Thus, neither OML nor ABR models are able to describe the dependence of the particle floating potential on plasma collisionality. At the same time, over the last several years there have been a number of investigations, including theories, experiments, and simulations, which clearly demonstrated that the largest variations in α (about one order of magnitude in some cases) can be associated with the plasma collisionality level [61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76]. The qualitative picture of the variation of the normalized potential α with plasma collisionality emerging from these studies is sketched in Fig.…”

Plasma flow around and charge distribution of a dust cluster in a rf discharge

“…Single dust grain simulations have investigated in detail the charging of the dust grain [6][7][8] , wake potential 4,[9][10][11] and the influence of the surrounding plasma properties like pressure 9,12 , ion speed 8,13,14 , charge exchange 12,[15][16][17] and inhomogeneties in the plasma sheath 9,18 . In twoparticle chains it has been found numerically that the negative charge of the downstream grain is reduced because the ion focus of the upstream grain increases the ion current onto the grain 19,20 .…”

DEMOCRITUS: An adaptive particle in cell (PIC) code for object-plasma interactions

“…Earlier versions of the DEMOCRITUS code (or of CELESTE2D from which DEMOCRITUS descends) were used in numerous previous studies [1,41,27,40,[42][43][44]. The changes presented here are sufficiently deep to require a rebenchmarking and only new original results are reported below.…”